This patch adds a selftest to show the usage of the new arguments in
cong_control. For simplicity's sake, the testing example reuses cubic's
kernel functions.
Signed-off-by: Miao Xu <miaxu@xxxxxxxx>
---
tools/testing/selftests/bpf/bpf_tcp_helpers.h | 23 +++
.../bpf/progs/bpf_cubic_cong_control.c | 176 ++++++++++++++++++
2 files changed, 199 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/bpf_cubic_cong_control.c
diff --git a/tools/testing/selftests/bpf/bpf_tcp_helpers.h b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
index 82a7c9de95f9..3115bc80280e 100644
--- a/tools/testing/selftests/bpf/bpf_tcp_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
@@ -21,6 +21,15 @@ BPF_PROG(name, args)
#endif
#define tcp_jiffies32 ((__u32)bpf_jiffies64())
+#define TCP_INFINITE_SSTHRESH 0x7fffffff
+
+#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
+#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
+#define FLAG_DATA_SACKED 0x20 /* New SACK. */
+#define FLAG_SND_UNA_ADVANCED \
+ 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
+#define FLAG_ACKED (FLAG_DATA_ACKED | FLAG_SYN_ACKED)
+#define FLAG_FORWARD_PROGRESS (FLAG_ACKED | FLAG_DATA_SACKED)
struct sock_common {
unsigned char skc_state;
@@ -37,6 +46,7 @@ struct sock {
struct sock_common __sk_common;
#define sk_state __sk_common.skc_state
unsigned long sk_pacing_rate;
+ unsigned long sk_max_pacing_rate;
__u32 sk_pacing_status; /* see enum sk_pacing */
} __attribute__((preserve_access_index));
@@ -86,6 +96,19 @@ struct tcp_sock {
__u32 prior_cwnd;
__u64 tcp_mstamp; /* most recent packet received/sent */
bool is_mptcp;
+ __u32 snd_cwnd_stamp;
+ __u32 mss_cache; /* Cached effective mss, not including SACKS */
+ __u32 high_seq; /* snd_nxt at onset of congestion */
+ __u32 packets_out; /* Packets which are "in flight" */
+ __u32 srtt_us; /* smoothed round trip time << 3 in usecs */
+ __u32 retrans_out; /* Retransmitted packets out */
+ __u32 lost_out; /* Lost packets */
+ __u32 sacked_out; /* SACK'd packets */
+ __u32 prr_delivered; /* Number of newly delivered packets to
+ * receiver in Recovery.
+ */
+ __u32 prr_out; /* Total number of pkts sent during Recovery. */
+ __u32 reordering; /* Packet reordering metric. */
} __attribute__((preserve_access_index));
static __always_inline struct inet_connection_sock *inet_csk(const struct sock *sk)
diff --git a/tools/testing/selftests/bpf/progs/bpf_cubic_cong_control.c b/tools/testing/selftests/bpf/progs/bpf_cubic_cong_control.c
new file mode 100644
index 000000000000..698964df1f33
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_cubic_cong_control.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/* WARNING: This implementation is NOT the same as the tcp_cubic.c.
+ * The purpose is mainly to show use cases of the new arguments in
+ * cong_control.
+ */
+
+#include <linux/bpf.h>
+#include <linux/stddef.h>
+#include <linux/tcp.h>
+#include "bpf_tcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+extern void cubictcp_init(struct sock *sk) __ksym;
+extern void cubictcp_cwnd_event(struct sock *sk, enum tcp_ca_event event)
+ __ksym;
+ extern __u32 cubictcp_recalc_ssthresh(struct sock *sk) __ksym;
+ extern void cubictcp_state(struct sock *sk, __u8 new_state) __ksym;
+ extern __u32 tcp_reno_undo_cwnd(struct sock *sk) __ksym;
+extern void cubictcp_acked(struct sock *sk, const struct ack_sample *sample)
+ __ksym;
+ extern void cubictcp_cong_avoid(struct sock *sk, __u32 ack, __u32 acked) __ksym;
+
+
+void BPF_STRUCT_OPS(bpf_cubic_init, struct sock *sk)
+{
+ cubictcp_init(sk);
+}
+
+void BPF_STRUCT_OPS(bpf_cubic_cwnd_event, struct sock *sk, enum tcp_ca_event event)
+{
+ cubictcp_cwnd_event(sk, event);
+}
+
+#define USEC_PER_SEC 1000000UL
+#define TCP_PACING_SS_RATIO (200)
+#define TCP_PACING_CA_RATIO (120)
+#define TCP_REORDERING (12)
+#define likely(x) (__builtin_expect(!!(x), 1))
+
+static __always_inline __u64 div64_u64(__u64 dividend, __u64 divisor)
+{
+ return dividend / divisor;
+}
+
+static void tcp_update_pacing_rate(struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ __u64 rate;
+
+ /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
+ rate = (__u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3);
+
+ /* current rate is (cwnd * mss) / srtt
+ * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
+ * In Congestion Avoidance phase, set it to 120 % the current rate.
+ *
+ * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
+ * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
+ * end of slow start and should slow down.
+ */
+ if (tp->snd_cwnd < tp->snd_ssthresh / 2)
+ rate *= TCP_PACING_SS_RATIO;
+ else
+ rate *= TCP_PACING_CA_RATIO;
+
+ rate *= max(tp->snd_cwnd, tp->packets_out);
+
+ if (likely(tp->srtt_us))
+ rate = div64_u64(rate, (__u64)tp->srtt_us);
+
+ sk->sk_pacing_rate = min(rate, (__u64)sk->sk_max_pacing_rate);
+}
+
+static __always_inline void tcp_cwnd_reduction(
+ struct sock *sk,
+ int newly_acked_sacked,
+ int newly_lost,
+ int flag) {
+ struct tcp_sock *tp = tcp_sk(sk);
+ int sndcnt = 0;
+ __u32 pkts_in_flight = tp->packets_out - (tp->sacked_out + tp->lost_out) + tp->retrans_out;
+ int delta = tp->snd_ssthresh - pkts_in_flight;
+
+ if (newly_acked_sacked <= 0 || !tp->prior_cwnd)
+ return;
+
+ __u32 prr_delivered = tp->prr_delivered + newly_acked_sacked;
+
+ if (delta < 0) {
+ __u64 dividend =
+ (__u64)tp->snd_ssthresh * prr_delivered + tp->prior_cwnd - 1;
+ sndcnt = (__u32)div64_u64(dividend, (__u64)tp->prior_cwnd) - tp->prr_out;
+ } else {
+ sndcnt = max(prr_delivered - tp->prr_out, newly_acked_sacked);
+ if (flag & FLAG_SND_UNA_ADVANCED && !newly_lost)
+ sndcnt++;
+ sndcnt = min(delta, sndcnt);
+ }
+ /* Force a fast retransmit upon entering fast recovery */
+ sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1));
+ tp->snd_cwnd = pkts_in_flight + sndcnt;
+}
+
+/* Decide wheather to run the increase function of congestion control. */
+static __always_inline bool tcp_may_raise_cwnd(
+ const struct sock *sk,
+ const int flag) {
+ if (tcp_sk(sk)->reordering > TCP_REORDERING)
+ return flag & FLAG_FORWARD_PROGRESS;
+
+ return flag & FLAG_DATA_ACKED;
+}
+
+void BPF_STRUCT_OPS(bpf_cubic_cong_control, struct sock *sk, __u32 ack, int flag,
+ const struct rate_sample *rs)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (((1<<TCP_CA_CWR) | (1<<TCP_CA_Recovery)) &
+ (1 << inet_csk(sk)->icsk_ca_state)) {
+ /* Reduce cwnd if state mandates */
+ tcp_cwnd_reduction(sk, rs->acked_sacked, rs->losses, flag);
+
+ if (!before(tp->snd_una, tp->high_seq)) {
+ /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
+ if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH &&
+ inet_csk(sk)->icsk_ca_state == TCP_CA_CWR) {
+ tp->snd_cwnd = tp->snd_ssthresh;
+ tp->snd_cwnd_stamp = tcp_jiffies32;
+ }
+ // __cwnd_event(sk, CA_EVENT_COMPLETE_CWR);
+ }
+ } else if (tcp_may_raise_cwnd(sk, flag)) {
+ /* Advance cwnd if state allows */
+ cubictcp_cong_avoid(sk, ack, rs->acked_sacked);
+ tp->snd_cwnd_stamp = tcp_jiffies32;
+ }
+
+ tcp_update_pacing_rate(sk);
+}
+
+__u32 BPF_STRUCT_OPS(bpf_cubic_recalc_ssthresh, struct sock *sk)
+{
+ return cubictcp_recalc_ssthresh(sk);
+}
+
+void BPF_STRUCT_OPS(bpf_cubic_state, struct sock *sk, __u8 new_state)
+{
+ cubictcp_state(sk, new_state);
+}
+
+void BPF_STRUCT_OPS(bpf_cubic_acked, struct sock *sk,
+ const struct ack_sample *sample)
+{
+ cubictcp_acked(sk, sample);
+}
+
+__u32 BPF_STRUCT_OPS(bpf_cubic_undo_cwnd, struct sock *sk)
+{
+ return tcp_reno_undo_cwnd(sk);
+}
+
+
+SEC(".struct_ops")
+struct tcp_congestion_ops cubic = {
+ .init = (void *)bpf_cubic_init,
+ .ssthresh = (void *)bpf_cubic_recalc_ssthresh,
+ .cong_control = (void *)bpf_cubic_cong_control,
+ .set_state = (void *)bpf_cubic_state,
+ .undo_cwnd = (void *)bpf_cubic_undo_cwnd,
+ .cwnd_event = (void *)bpf_cubic_cwnd_event,
+ .pkts_acked = (void *)bpf_cubic_acked,
+ .name = "bpf_cubic",
+};
--
2.43.0
